Vehicle safety restraint systems for detecting the occurrence of a vehicle crash and actuating a safety restraint in response to such a detected crash are known in the art. Such systems often include an accelerometer mounted to the vehicle. A controller, such as a microcomputer, monitors the accelerometer output. The controller includes an algorithm that is used to discriminate, based on accelerometer output, between a deployment crash event for which the safety restraint is to be actuated and a non-deployment crash event for which the safety restraint is not to be actuated. These algorithms are known as "crash metrics". Certain known crash metrics monitor crash velocity as a function of time or crash displacement as a function of time based on the acceleration. If crash velocity or crash displacement exceed associated threshold values, the restraint is actuated. It is known to have fixed thresholds or thresholds that vary as a function of time.